Reinforced reconstituted tobacco sheet



United States Patent 3,459,195 REINFORCED RECONSTITUTED TOBACCO SHEETHenri C. Silberman, Richmond, Va., assignor to Philip MorrisIncorporated, New York, N.Y., a corporation of Virginia No Drawing.Filed June 16, 1966, Ser. No. 557,917 Int. Cl. A24b 3/14, 13/02 U.S. Cl.13117 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates totobacco compositions and methods of producing such compositions. Moreparticularly, the invention relates to improved reconstituted tobaccosheets which are reinforced in such a manner that their physicalproperties are greatly improved without the decreases in smokingqualities.

During the production and processing of tobacco products, includingaging, blending, sheet forming, cutting, drying, cooling, screening,shaping and packaging, considerable amount of tobacco fines and tobaccodust are produced. It is known that such tobacco fines and dust can becombined with a binder to form a relatively coherent sheet, whichresembles leaf tobacco and which is commonly referred to asreconstituted tobacco. Various methods have been employed for makingreconstituted tobacco of this general character. For example, one methodfor making reconstituted tobacco is disclosed in United States Patent2,734,510 wherein the tobacco fines and dust are applied to a bindermade of carboxymethyl cellulose, carboxymethyl hydroxyethyl cellulose ora suitable salt thereof. Other patents, such as United States Patent2,708,175 and United States Patent 2,592,554 described various otherbinders which may be used in the production of reconstituted tobacco.There are also numerous other methods which have been employed for theproduction of reconstituted tobacco.

All of the presently known methods for producing reconstituted tobacco,however, involve the production of reconstituted tobacco sheets whichwould be improved if there were some way of further increasing theirstrength, without deleteriously affecting any of their other desirableproperties. Many reconstituted tobacco sheets, produced in accordancewith the teachings of the prior art, have been found to be undesirablyweak, both during the actual steps involved in their preparation andduring the processing steps involved during their incorporation insmoking products.

One method which is used in the trade for producing sheet from tobaccoscraps is to reduce the tobacco to dust, to lay down a layer of thisdust, and to apply to it a layer of liquid binder solution orsuspension, on top of which another layer of dust is laid. Sometimes, asecond layer of binder and athird layer of dust are applied, theresulting sheet is lacking in strength and must be handled with greatcare. If it is made too Patented Aug. 5, 1969 thick, it will not have atobacco-like appearance and is likely to burn improperly.

I have discovered that a reinforcing base in the form of a gauze or webmay be used on which to apply tobacco dust, to form a reconstitutedtobacco sheet of good strength and filling power and to result in asmoking product having an acceptable smoke flavor. I have also foundthat the novel products produced in accordance with my invention, whensmoked, produce smoke which contains smaller amounts of certain of theless desirable components found in tobacco smoke than the smoke whichresults from the usual reconstituted tobaccos or the smoke which resultsfrom natural tobacco.

My invention comprises using, as a base for reconstituted tobaccosheets, a gauze or web of cellulose which has been treated in such a waythat its combustion and pyrolysis characteristics are modified. Thismodification is evidenced by a reduction in the static burning rate ofthe resulting product, as will be discussed in more detail below.

Cotton (cellulose) gauze will burst into flame, under ordinaryconditons, when it is ignited. By appropriate lowering of the burningrate of the cellulose, for example, by oxidizing the cellulose or by theapplication of certain flameproofing agents to the cellulose, or byimpregnating the cellulose with tobacco solubles, the web of treatedcellulose can be combined, as will be described in more detail below,with tobacco parts to make a reconstituted tobacco product which willglow or burn at a rate similar to the burning rate of ordinary tobaccofiller.

The lowering of the burning rate of the treated cellulose web to beemployed in accordance with the present invention, should be such thatthe static burning rate of a cigarette produced in accordance with thepresent invention, and including the treated cellulose in combinationwith tobacco in the amounts specified below, will be more than 2millimeters per minute. The static burning rate of a cigarette(non-filter with an RTD of 1.8-2.8 inches of water) containing oxidizedcellulose or cellulose treated with flame retardants, the cellulose notbeing in combination with tobacco, will be 2 millimeters per minute orless up to the point where no burning will occur. The static burningrate is the burning rate, without any pufiing, of a standard sizecigarette and is defined as the millimeters of cigarette which areburned per minute, when the test cigarette is statically burned in acontrolled draft cabinet. By comparison, the static burning rate ofcommercially available cigarettes is approximately 4 to 5 mm. perminute.

While an excess of the treating reagent may be employed to reduce thestatic burning rate of the cellulose even further below the 2 mm. perlimit level, it is preferred that only suflicient reagent be employed todecrease the static burning rate to approximately 2 mm. per minute.

Particulate tobacco, for example, tobacco which has been pulverized andwhich has been homogenized in water, or tobacco which has received anenzyme treatment in accordance with the teachings of U.S. Patent3,240,214, or tobacco which has been slurried with an added binder, isapplied to said gauze. The tobacco material may be applied to one orboth sides of the base gauze by rolls, by a spray, or by a dip, afterwhich the resulting sheet is dried.

Such products have been found to be self-supporting even before drying.They can be cut into sheets for shredding into filler for smokingarticles or rolled for use as cigar binder. They have also been found tohave the strength to permit shredding, blending, cigarette making andany other necessary handling. They have good filling power, whenshredded as cigarette filler, and good smoking qualities. They alsoprovide a light, sweet smoke,

which may be less harsh than that of most commercial reconstitutedtobacco.

The cellulose web which is employed in the present invention may beeither woven or non-woven, but is preferably of a thin, openconstruction, having, for example, a weight of from 14 to 45 g./sq. yd.,and having from 15 to 50 threads per inch, if woven. The mesh size ofthe gauze should be sufiiciently coarse for a tobacco slurry topenetrate at least partially into the interstices of the web. Thisaffords a more intimate mixture of the tobacco material with thecellulosic matrix and results in a better adhesion of the tobacco to thematrix. The mesh size also should be sufficiently fine so thatreinforcement is still attained for the material in the shredded form.Each shred of the reinforced tobacco in a cigarette should, preferably,contain some reinforcing cellulosic material. If the weaves are tooopen, too many shreds containing no reinforcing matrix might result. Onegauze which has been satisfactorily employed had 18 weaves per inch andweighed 18 g. per sq. yd., another gauze which has been satisfactorilyemployed had 42 weaves per inch and weighed 39 g. per sq. yd.

If oxidation of the cellulose is to be employed, an agent such asnitrogen dioxide is selected which will produce carboxyl groups withoutseriously affecting the mechanical properties of the material. Theoxidation or other treatment may be applied either before or after theweb is formed. The carboxyl content may be from 10 to 24% afteroxidation.

The oxidation technique which may be employed is preferably theoxidation of cellulose by nitrogen dioxide which occurs mainly accordingto the following equation:

The following descripiton is an illustration of the preparation ofoxidized celluloses which are suitable for use in accordance with thepresent invention:

Commercial nitrogen dioxide was introduced into a reaction vesselcontaining cellulose. The ratio of N to cellulose was chosen between 1:1and 7:1. The vessel was closed and the reaction was allowed to takeplace at room temperature for from one to days. At the end of this timeas much nitric oxide (NO) and excess nitrogen dioxide (NO as possiblewere removed by evacuation. The oxidized cellulose was taken out of thevessel and plunged into distilled water, after which it was washed withnumerous changes of distilled water and dried. Its nitrogen content wasfound to be between 0.05 and 1.0% and its carboxyl content was found tobe between 10 and 22% by weight. The theoretical maximum carboxylcontent, assuming that only the one hydroxyl group per anhydroglucoseunit in the above equation is oxidized, would be 25.6%. The procedurefor the oxidation of cellulose by nitrogen dioxide has been described inthe literature, for example, in Methods in Carbohydrate Chemistry,volume III, Roy L. Whistler, editor, Academic Press, New York 1963, pp.168-172. One type of oxidized cellu- 1 At a carboxyl content above 22%the oxidized gauze loses tensile strength.

lose which is commercially available may be obtained from EastmanChemical Products Inc., Kingsport, Tenn.

Oxidized cellulose prepared in the above manner, and containing 20%carboxyl groups has been subjected to thermal degradation and the weightloss has been compared as a function of the temperature. The followingprocedure was followed. A 10 g. sample was weighed into an aluminumdish, placed in a vacuum oven, heated up to the desired temperature andkept one hour at this temperature. The sample was then removed from theoven and weighed again. The experiments were performed under vacuum orby passing air, nitrogen or argon, through the oven. The results of theexperiments are summarized in Table I. As can be seen from Table Ibelow, oxidized cellulose is converted at 200 mostly into volatileproducts, while the cellulose is barely degraded.

TABLE I Residual weight after one hour at; 200 C. in air, nitrogen,argon or vacuum (g.)

Weight before Material experiment (g.)

Cellulose (Johnson & Johnson It can be seen from Table I that, unlikecotton cellulose, oxidized cellulose yields very little tar onpyrolysis. The gaseous products from the pyrolysis of oxidized cellulosehave been identified as consisting mainly of H 0, CO and CO. It can alsobe concluded from Table I that oxidized cellulose, while conferringmechanical strength to the unlit product, is degraded at temperaturesbelow the burning temperature of tobacco in a cigarette into morefavorable volatile products and into less tar than cotton cellulose. Forexample, as is demonstrated in Example 5 which appears hereinafter,oxidized cellulose in a cigarette delivers less than half the amount ofacetaldehyde and about a tenth the amount of benz(a)pyrene as comparedto cellulose.

If flameproofing of the cellulose is to be employed, some of theflameproofing agents which may be used to treat the cellulose base, inaccordance with the present invention, are diammonium phosphate,tetrakis (hydroxymethyl) phosphonium chloride (also referred to asTHPC), phytic acid, ammonium sulfate, diammonium phosphate with urea,and pentaerythritol with phosphoric acid.

When cotton is treated with one of the many commercially available flameretardants, such as the retardants mentioned above, then shredded andblended with tobacco into a cigarette, it does not participate in thecombustion and has many undesirable properties. For example, thecigarette does not burn evenly, the ash does not hold together. Cottontreated with flameproofing compounds and coated with tobacco andthereinafter shredded, gives a more satisfactory smoke. The reason seemsto be that the tobacco portion furnishes the heat for combustion Whilethe cotton treated with flame retardants pyrolyzes in a manner differentthan untreated cotton. The various reaction mechanisms which take placeare very complex. Flameproofing agents are believed to act by a coatingeffect, by a thermal effect, by a gaseous effect and/or by a chemicaleffect. In the context of this invention, it is of importance that theflameproofing compounds are nontoxic and do not produce undesirable ortoxic volatiles upon pyrolysis. It is also of importance that theapplication of desirable flame retardants to cellulose decreases theamount of tar and increases the amounts of gas and char from thecellulose formed on pyrolysis. A desirable flame retardant according tomy invention incorporates strength to the unlit reconstituted tobacco;during combustion the flame retardant increases the amount of ash,without causing the static burning of cigarettes made employing theflame retardant treated tobacco to stop and without releasingundesirable gaseous or undesirable particulate compounds, i.e., tar. Thefollowing general classes of compounds may be employed as flameretardants within the context of my invention: Boric acid and borates;chlorides, phosphates, sulfates, bromides, fluorides, formates andcarbonates of the following metals: calcium, magnesium, aluminum,lithium, zinc, potassium, sodium, barium and strontium, as well asammonium. Organic flame retardants containing phosphorous may also beused.

When a fiameproofing agent is used, it is applied to the cellulose in anamount comprising from about 1 to 30% by weight, based on the cellulose,and it may be applied by one of the many processes which are used forthe flameproofing of cellulosic material. For example, a solution of theflameproofing reagent is added to the cellulose matrix by immersion ofthe cellulose into the solution, the excess solution is removed bysqueezing or centrifuging, the product is dried at 45 to 109 C., and isthen cured, if necessary, at 110 to 170 C. As an illustration, thecellulose-phosphate-urea reaction was brought about by followingessentially the method described by A. C. Nuessle, F. M. Ford, W. P.Hall and A. L. Lippert (Textile Research Journal, volume 26, 1956, p.32). The cellulosic fabric was immersed in a water solution containingbetween 4 and 40% urea and between 2 and 20% (NH HPO squeezed, dried andbaked 10 min., at 150 C., washed in water to remove unreacted materials,and dried.

In other instances a solution of the reagent was added to the cellulosematrix by immersion, whereupon the treated cellulose was squeezed anddried at 45 C. in a forced air circulation oven before the applicationof tobacco. Other treatments will be described in the examples whichappear later in this specification.

The flameproofing agent is not generally employed with oxidizedcellulose, although combinations of flameproofed cellulose and oxidizedcellulose may be employed.

If intimate mixing of the cellulosic matrix with tobacco solubles is tobe employed, the cellulosic matrix can be immersed in tobacco solublesor the tobacco to be applied to the matrix can be processed as torelease solubles into the matrix.

Tobacco solubles can be obtained by extracting tobacco with water,alcohol or other suitable solvents. Another way of releasing tobaccosolubles besides extracting which I used was the treatment of tobaccomaterial with enzymes that can break down the cell walls. It was foundthat by using catalytic amounts of enzyme, for example, preparationshaving cellulase, hemicelluase and pectinase activity, the tobaccosolubles inside the cells are released and no unfavorable aroma isimparted to them. At the same time, a tobacco slurry is obtained thatcan easily be applied to a cellulosic matrix and adheres Well afterdrying. When tobacco solubles are employed in accordance with thepresent invention, the water or alcohol soluble extract is obtained byWashing tobacco at a temperature of from about room temperature to 100C. for example, for a period of from about 5 to 120 minutes, and shouldbe applied to the cellulose in amounts of from 1 to 20% by weight basedon the cellulose. It may be applied by immersing the cellulose matrix ina solution of tobacco solubles, by spraying or the like.

The tobacco dust may be prepared from any stems, (i.e., tobacco leafmidribs), scraps, fines or combination of these, and is preferablypulverized to pass at least a SO-mesh screen but with no limit onfineness. With the proper choice of a coating system, larger mesh size,for example mesh tobacco, could be utilized. The dust may be slurried inwater with an enzyme having cellulase, hemicellulase, and pectinaseactivity, the pH being adjusted to 4.2-5.0, for example, with citricacid, if necessary, and the slurry may be digested either for 3 to 20hours at room temperature or for to 12 hours between about 45 C. andabout 80 C. In a different procedure, the tobacco slurry without enzymemay be homogenized, that is, milled to much finer dimensions (e.g., in aManton-Gaulin homogenizer). Alternatively, a binder may be added to theslurry. Such binders as are commonly used in preparing reconstitutedtobacco include natural gums, pectins, methyl cellulose andcarboxymethyl cellulose. Usually, a humectant such as glycerol,propylene glycol, or triethylene glycol is added, but its presence isnot essential; humectants from O to 10% of the tobacco weight may beused.

The tobacco slurry may be applied to the treated gauze by any of theknown methods such as casting, rolling, spraying or dipping, and may beapplied to one or both surfaces. The resulting tobacco-containing sheetmay then be dried by conventional means, for example, in small scaleoperations by air at room temperature or by air drying at a moreelevated temperature, such as 45 C. to C., until the moisture content isbrought to the proper level, which is approximately 11 to 14% by weight.In large scale commercial operations, with forced air circulation at atemperature of from about 315 C., a drying time of about one minute orless will, generally, be sufiicient. The finished sheet appears uniform,smooth, medium to dark brown in color.

The finished product may be shredded by conventional means and, afterbeing shredded, may be mixed with tobacco for use as cigarette filler.It may also be used unblended, in which case it is necessary that thetreated cotton portion of the reinforced reconstituted tobacco sheetcomprises 5 to 50% by weight and, preferably, from 10 to 35% by weight,according to the degree of resistance-to burning possessed by thetreated cotton, in order that the shredded reinforced reconstitutedtobacco sheet support combustion. If the product is to be blended withtobacco, or used as a cigar binder, the proportion of reinforcement maybe higher, up to 70% of the sheet.

The following examples are illustrative:

Example 1 Cotton gauze was oxidized by dry nitrogen dioxide by themethod which has been described in the literature (E. C. Yackel and W.O. Kenyon, J. Am. Chem. Soc. 64, 121-127 (1942)). Cotton gauze, Steripadbrand 50 g., produced by Johnson and Johnson Co. was packed loosely in areaction flask. From a supply of about g. of nitrogen dioxide, nitrogendioxide vapor was circulated over the gauze in the reaction flask. Thevapor leaving the reaction vessel passed to a water-cooled condenser andwas returned as unreac'ted nitrogen dioxide to the supply flask. Afteran initial slight temperature rise, the reaction vessel returned to roomtemperature (23 C.). This pro cedure was continued for about 15 hours;nitrogen oxides were then removed from the gauze by a flow of air, andthe product was rinsed rapidly in distilled water until the washingswere no longer acidic, and dried in air.

A dust of pulverized tobacco containing stern and leaf was slurried inwater with 0.1% of the tobacco weight of Cellulase 35 enzyme anddigested overnight. The slurry was stirred rapidly and was cast onoxidized cellulose gauze taped to a glass plate to give a sheet which,after drying to 12% moisture, contained 68% tobacco materials. Thissheet, 0.017 in. thick, had a tensile strength of 4.0 kg./sq. in., anelongation of 7.8% and a work to-break of 577 g. cm./sq. in.(Work-to-break is the work required to elongate and break a unitcross-section of sheet.) A commercial reconstituted tobacco productprepared from similar tobacco scrap was 0.012 in. thick, had 0.51kg./sq. in tensile strength, 2.8% elongation, an work-to-break of 22.4g. cm./sq. in. Sheet cast from the treated tobacco dust withoutreinforcement was 0.007 in. thick, had a tensile strength of 0.39kg./sq. in., an elongation of 5.0% and a work-to-break of 33.0 g. cm./sq. in.

2 Cellulase 35 enzyme is produced by Rohm and Haas (30., Philadelphia,Pa. and 1s a mixture of polysaccharases includrng cellulase, pectmaseand hemi-cellulase.

The reinforced sheet handled well, and shredded without excessivebreakage to give a filler which, when smoked, had good aroma and mildtaste.

It can be seen from the above that reconstituted tobacco reinforced byoxidized cellulose gauze has greater mechanical strength than thecommercial reconstituted tobacco material presently used in cigarettefiller. This mechanical strength is due to the cellulosic matrix ratherthan to the tobacco slurry which, when cast on glass plates, has beenfound to produce sheets of about the same mechanical strength as acommercial reconstituted tobacco material.

Example 2 In a one-gallon Waring Blendor container, 0.2 g. of Cellulase35 enzyme was added to 2000 ml. of water. After brief stirring todissolve, 200 g. of 50 mesh dust of tobacco by-products, composed of 50%bright stems and 50% leaf blend, was added and stirred to disperse. ThepH was adjusted to the range of 4.2-5.0 by adding approximately one g.of citric acid monohydrate; of glycerine, 10 ml., was added ashumectant. The slurry was allowed to stand three hours at roomtemperature. It was stirred at maximum speed for one minute and thethick slurry was diluted with water as required for castmg.

A piece of commercial oxidized cellulose gauze (having a carboxylcontent of 19%, and produced by Eastman Chemical Products, Inc.,Kingsport, Tenn.) weighing 11.5 g. was stretched and taped on a glassplate.

A portion of the slurry of tobacco dust was cast on the gauze, and thecombination was dried in a forcedair circulation oven at 45 C. for threehours. The finished sheet (comprising 33 cellulosic base) which wasstripped oil? the glass plate weighed 34.5 g.

As control sheets were cast from another portion of the slurry withoutsupport and the sheets were dried at 45 C., the sheets were shredded andmade into cigarettes each of which was 65 mm. in length and had aresistanceto-draw (RTD) of 1.8-2.2 in. of water. The resultingcigarettes were presented to a smoking panel consisting of five expertsmokers. The panel found the product of the invention to have a verymild and sweet smoke. The comparative results which were found are givenin Table II.

TABLE II.-SMOKING EVALUATION OF RECONSTITUTED TOBACCO CIGARETTES 1 RTDis defined as the pressure drop across a cigarette, expressed as inchesof water, when air flows through the cigarette at a velocity of 1,050m1./min. To determine this pressure dilference, one end of the cigarettewas inserted into a specially designed tube through which air was drawn.The pressure difference between the open and enclosed ends of thecigarette was measured.

2 Very mild, high in basic sweet.

Example 3 In a similar manner to that described in Example 2, a tobaccoslurry in enzyme solution was made up. A portion of the slurry was caston Steripad cotton gauze weighing 20.0 g. to give a sheet which, whendry, weighed 107.5 g. A portion of the slurry was cast on commercialoxidized cellulose gauze weighing 14.5 g. to give a sheet weighing 51.0g. when dry.

The resulting sheets were shredded and each was blended with an equalweight of a commercial cigarette tobacco. Cigarette rods made from theseblends were 65 mm. long, weighed 1.1 g., and had resistance-to-draw of2.0 to 2.2 inches of water. Commercial ZO-mm. cellu- TABLE III.SMOKINGPANEL EVALUATION OF BLENDS OF RECONSITIIUED TOBACCO Enzyme-treatedEnzyme-treated tobacco dust on tobacco dust on cotton gauze oxidizedcellulose and tobacco and tobacco Percent cellulosic reiniorce- 9 14.

ment.

Panel result More sour and More hay-tobacco,

woody, more more thinoverall harshbodied, more ness. metallic.

Example 4 Hand-made filter cigarettes of same make-up (identical filter,same RTD) were prepared and submitted to a panel of five expert smokers.

In one set of experiments increasing amounts of Whatman No. 1 cellulosepowder was added to a homogenate of cigarette tobacco. In another set ofexperiments increasing amounts of Steripad cotton gauze shreds(cellulose) was added to cigarette tobacco. The results of the panelevaluation are summarized below. It can be seen that high amounts ofcellulose powder intimately mixed with tobacco solubles can be toleratedwhile already small amounts of gauze shreds produce an undesirable harshsmoke.

COMPARISON OF SMOKE FLAVOR PROFILES Control 100 parts 01' homogenizedtobacco blend, no added cellulose.

Experimental 100 parts of homogenized tobacco blend parts cellulosepowder; less taste less burnt, less mouth harshness less astringent,more throat harsh acrid.

Do parts of tobacco blend, 80 parts of cotton gauze shreds; could not besmoked because too harsh.

These results show that intimate mixing of cellulose with tobaccosolubles greatly decreases the harshness of smoke delivered from purecellulose.

Example 5 Various hand-made non-filter cigarettes of identical lengthand RTD were examined for acetaldehyde delivery according to an infraredabsorption procedure and for benzo(a)pyrene delivery. A commercialtobacco blend was used in the making of the cigarette. It was also usedfor producing an aqueous tobacco extract in which Steripad cotton gauzeand oxidized cellulose were dipped. A cigarette containing 100%untreated cotton gauze burns with a flame; a cigarette containing 100%untreated oxidized cellulose gauze does not burn at all. The treatmentwith tobacco solubles decreases the burning rate of cellulose andincreases the burning rate of oxidized cellulose to reach roughly thesame rate (3 to 5 mm./min.). The acetaldehyde analyses of the smoke gasphase are summarized in the table below. The results indicate thatcellulose in the form of gauze shreds or extract containing cotton gauzedelivers about the same amount of acetaldehyde into smoke. Oxidizedcellulose, however, on the same weight basis delivers less than half theamount of acetaldehyde than does untreated cellulose. Benzo(a)pyrene wasisolated by column chromatography and paper chromatography of theparticulate phase of cigarette smoke. The

Acetaldehyde, Benzo(a)pyrene micrograms/cig. 1 ,g./cig.

Cigarette filler 100% tobacco blend Blend of 60% tobacco blend and 40%untreated cotton gauze (cellulose) shreds Blend of 60% tobacco blend and40% cotton gauze with 33% tobacco solubles Cotton gauze (cellulose) 6%tobacco solubles 100% oxidized cellulose (10% carboxyl content) gauzewith 6% tobacco solubles Blend of 60% oxidized cellulose gauzecontaining 6% tobacco solubles and 40% tobacco blend.

N .D.-Not determined.

Example 6 Cotton gauze, Steripad, weighing 25.0 g was treated with aflameproofing agent consisting of 20 g. urea and g. diammonium phosphatein 100 ml. of water. The gauze was dried and cured 10 min. at 150 C.; again in weight of 8.8 g. was observed.

A slurry prepared from tobacco dust, as described in Example 2, wasapplied to one side of this gauze. The sheet which, after drying,contained 32% of reinforcing gauze was shredded. When made intocigarette rods, 65 mm. long, weighing 0.8 g. and having 2.1 inch RTD,and attached to a commercial cellulose acetate filter, it burned Welland with a pleasant aroma. The smoke contained 18.7 mg. of totalparticulate matter (TPM) and 8.3)(10' g. of benz(a)pyrene (0.44 ppm. inthe TPM). A commercial cigarette of average benz(a)pyrene delivery, withthe same length of rod and filter delivered 20.1 mg. of TPM and l1.7 10g. of benz(a)pyrene (0.59 ppm.) The results show that the cigarette withthe reinforced flameproof cotton matrix delivered less benz(a)pyreneinto smoke than the control Example 7 Cotton gauze (Steripad gauze), 51g., was dipped into a solution containing 40 g. urea and 20 g.cliammonium phosphate (DAP) dissolved in 100 ml. water. The wet gauzewas squeezed, air-dried and cured for 10 min. in an oven heated at 150C. A weight gain of 48 g. was observed. A double layer ofDAP-urea-treated gauze was coated on one side with enzyme-convertedtobacco dust slurry as previously described and air-dried. The sheet wascomposed of 39.6% DAP-urea-treated cotton and 60.4% tobacco material.This product was coded A. A portion of A, 52.5 g., was then coated withenzyme-converted tobacco slurry on the tobacco free-side, air-dried andweighed. The weight was 61.5 g.; its composition was 20.8 g. (33.8%)DAP- urea-treated cotton gauze and 40.7 g. (66.2%) tobacco material Theproduct was coded B.

Unmodified Steripad gauze, in double layers, was coated on one side withenzyme-converted tobacco dust slurry as previously described andair-dried. The final sheet was composed of 26.7% cotton and 73.3%tobacco material. It was coded C.

Enzyme-converted tobacco dust slurry was also cast on glass plates andair-dried. The resulting sheets were coded D.

The mechanical strength of the samples A through D RECONSTITUTED,TOBACCO MATERIAL AT 12% MOISTURE Sheet Instron Elongation Work, g.

Material weight, tensile, at break cm./in.

g./tt. kg./in. percent N.D.-Not determined.

The results show a considerable increase in tear strength due to thevarious gauze reinforcements.

Example 8 A matrix support was prepared from cotton cheese cloth (Curitygrade 90, manufactured by the Kendall Co., New York 18, New York) andphytic acid (70% aqueous solution, from Nutritional BiochemicalCorporation, Cleveland, Ohio). Phytic acid (inositol hexaphosphoricacid, C H O P occurs in nature usually in the form of the mixed calcium,magnesium and potassium salt. The product of commerce is mostly derivedfrom corn steep liquor.

Cheese cloth (172.5 g.) was dipped into a solution of 70 g. phytic acidin 300 ml. water, squeezed and air-dried. The weight gain was 65 g. Ontothe phytic acid-treated cloth was cast enzyme-treated tobacco slurry asdescribed in Example 2. The dry material contained 30.5% phyticacid-treated cotton. This sheet was shredded and made into filtercigarettes. The cigarettes contained 1.0 g. filter per cigarette and hadan RTD of 4.0 inches of water without and of 6.0 with filter. Thecigarettes were coded A.

Cigarettes of the same weight and RTD as those coded A were also madefrom unmodified cheese cloth coated with the tobacco slurry. In thiscase, the filler was composed of 22.5% cotton. The filter cigaretteswere coded B.

The values in Table V (below) are absorption values obtained frominfrared analysis of the smoke gas phase. They are thus relative values.For comparison, a typical commercial filter cigarette (0.85 g. fillerweight, RTD=4.7 inches with filter) was also analyzed. It was coded C.

TABLEV.INFRARED ANALYSIS OF GAS PHASE OF SMOKE v Acetalde- CarbonCigarette hyde monoxide Isoprene Acetylene Methane TABLE VI.DESORIPTIVEPANEL SMOKING Cigarette Harshness Flavor A Less harsh than B Svgeet,1%1016 acceptable flavor B Hot to tongue and nose--. Burn vegetables,dusty.

Cigarette A was found to be less harsh and to have a sweeter, moreacceptable flavor than B, which was hot and dusty.

Example 9 To 15 gal. of water 0.67 lb. of guar gum (General Mills,Minneapolis, Minn.) was added with stirring and the mixture was heatedto C. for 15 min. Then 0.67 lb. of Methocel MC (methyl cellulose, 4000cps., Dow

Chemical Co., Midland, Michigan) was stirred in and the mixture wasallowed to cool. The following were added in sequence: triethyleneglycol, 0.6 lb.; carboxymethylcelluose 7 MP (Hercules Powder Co.,Wilmington, Delaware) 0.67 1b.; and 17.4 lb. tobacco dust, 50 mesh. Themixture was blended in a Cowles dissolver for 10 minutes.

Cotton gauze prepared as in Example 8 by treatment with phytic acid wascoated with the tobacco slurry and the sheet was dried. It had goodstrength, and when shredded and blended with tobacco in equal parts, itgave a satisfactory mild smoke.

Example 10 A pentaerythrityl phosphoric acid ester of cellulose wasprepared following essentially the method set forth in US. Patent2,592,544.

Into a 500 ml. beaker was added 20 grams of urea, and while stirringwith a glass rod, 19.3 g. of 85% orthophosphoric acid. The mixture washeated on a hot plate until a uniform solution was formed. Water, ml.,and pentaerythritol, 5 grams, was added with a pipette. The beaker wasput into an oven at 150 C. and kept there for 90 min. The product wasleft to cool and was collected in a jar. To a solution of 15 grams ofthe product in 35 ml. of water was added 15 grams of urea and letdissolve. Steripad gauze, pads weighing a total of 25.0 grams was dippedinto the solution, squeezed, air-dried and cured for minutes at 140 C.The cured gauze was washed in water and air-dried. It weighed 27.5 g.The gauze did not burn when lighted with a match. It has become flameresistant. Chemical analysis showed it to contain 1.4% total nitrogenand 0.5% total phosphorus. The gauze was coated on one side with aslurry of Cellulase 3.5modified tobacco dust (50% leaf 50% midrib) inthe way described before. The ratio flameproof gauze to tobacco was 1 to2. The reinforced tobacco was shredded and made into cigarrettes. Thecigarettes burned very well and had a pleasant smoking aroma.

Example 11 Filter cigarettes of the following different compositions butwith identical resistance-to-draw, filter, and make-up were prepared andsubmitted to a panel of 5 expert smokers.

(A) A uniform blend of 25% shredded untreated Steripad cotton gauze and75% shreds of a thinly cast sheet obtained by treating -50 mesh tobaccodust composed of equal parts of tobacco leaf and tobacco leaf midribwith Rohm and Haas Cellulase 35, water, citric acid and glycerine asdescribed before.

(B) A uniform blend of shreds of 40% of the above gauze and shreds of60% of the above cast sheet.

(C) A 100% blend of Steripad gauze coated with the same tobacco slurrywhich was used to cast the sheets of cigarettes A and B. The ratio gauzeto tobacco was 1 to 3.

(D) A 100% blend of phytic acid-treated cheese cloth coated with thesame tobacco slurry which was used to make cigarettes A, B and C. Thecheese cloth matrix contained 25% of phytic acid, the ratio of phyticacid-treated cloth to tobacco was 1 to 2.4 (42% treated cloth, 58%tobacco).

(E) A 100% blend of Steripad cotton gauze made flameproof withdiammonium phosphate-urea and coated with the same tobacco slurry whichwas used for making cigarettes A to D. The treated Steripad matrixcontained 22% of (NH HPO -urea and 78% of cellulose. The ratio offlameproof gauze to tobacco was 1 to 2.

The panel results were as follows:

A-very harsh to tongue and throat, cannot be inhaled.

B-harsher and hotter than A.

Cmilder than A or B; better flavor.

Dsweet aromatic; milder than A or B; in general preferred to A, B or C.

12 E-milder than A or B; delivers less smoke; slight metallic note.

This example indicates that the smoke from a cigarette in which thecellulosic matrix is intimately mixed with tobacco is much milder thanthe smoke from a cigarette in which the cellulosic material is blendedwith tobacco. It also indicates that a cigarette containing a matrix ofnon-combustible cellulose is preferred over a cigarette containing ablend of cellulose and tobacco.

Example 12 Curity No. 10 cheese cloth (Kendall Co., 20 x 12 webs/ sq.in.), 29 grams, was added to 600 ml. water in a 2 liter beaker. Amixture of 7.2 ml. THPC (Tetrakis (hydroxymethyl) phosphonium cholride)and 2.4 ml. triethanolamine was added. The gauze was stirred for 15minutes. NH Cl, 5 grams, was added; the pH was 4.1. A total of 25 gramsof anhydrous sodium pyrophosphate (Na P O dissolved in 500 ml. of waterwas added slowly to bring the pH up to 7.5. The mixture was heated to 88C. NH OH conc., 6 ml., was added. After cooling, the treated gauze waswashed with water, dried and cured at 138 C. for 5 minutes. The materialwas washed again and dried. The material did not burn when lighted witha match. An analysis of this flameproof material revealed a total ashcontent of 1.4%, an insoluble phosphorous content of 0.12% and aninsoluble nitrogen content of 0.25%. Equal amounts, 10 g. each, ofTHPC-treated and THPC-untreated material were heated in an oven for 105minutes at 390 C. in the presence of air. The residue (char) of thetreated material weighed 3.3 g. while the residue of the control weighed0.3 g. THPC treatment has increased the char formation and this is aclue that pyrolysis of cotton treated with THPC occurs differently thanpyrolysis of untreated cotton.

In a related experiment 30 grams of Curity No. 10 cheese cloth wasimmersed in an aqueous solution of diammonium phosphate. The gauze wassqueezed to remove excess solution and dried. The dry material weighing34.5 grams was pyrolyzed at 390 C. in the presence of air. The residue(char) weighed 10.0 g. of which not more than 4.5 g. can be inorganicmatter. A control sample of 30 grams Curity No. 10 cheese clothpyrolyzed together with the treated sample yielded a residue of only 2.3g.

Example 13 A double layer of Steripad cotton gauze of total weight 50 g.was coated with one layer of enzyme-treated tobacco dust in the mannerdescribed in Example 11.

The dry, trimmed, reinforced material was composed of 43.5 g. originalcotton gauze and 130.5 g. tobacco material. Tobacco solubles had fullypenetrated the cotton gauze. Filter cigarettes were made from of thereinforced material. They contained 0.8 g. filler each and had an RTD of5.0-6.0 with the filter. The cigarettes delivered 9.510.9 g.benzo(a)pyrene per cigarette. In a control experiment cigarettes wereprepared containing the same ratio of gauze (25 to tobacco material (75However, the enzyme-treated tobacco dust was cast separately intosheets. Shreds of the cast tobacco sheet were blended with shreds of thecotton gauze. The cigarettes contained 1.1 g. filler and had an RTD of5.0-6.0 with the filter. The cigarettes delivered 18.10 g. benzo(a)pyrene per cigarette, thus twice as much as the cigarettes fromreinforced reconstituted tobacco.

Example 14 Oxidized cellulose gauze (Eastman Co., l622% carboxyl) 21 g.was covered with one layer of enzyme-treated tobacco dust from 100%leaves in a manner identical to the one described in Example 11.

The dry reinforced reconstituted tobacco contained 18 g. of the originalgauze and 53 g. of tobacco material. The sheet was shredded and madeinto non-filter cigarettes of RTD 3.4-4.0 and filler weight 1 g. Thecigarette yielded 8 puffs per cigarette on a smoking machine and had astatic burning rate of 4 mm./ min. The phenols delivery was 22.10g./cigarette and the nicotine delivery was 0.39-10 g./cigarette. In asimilar experiment Steripad cotton gauze was used with the sameenzyme-treated tobacco slurry. The dry reinforced reconstituted tobaccocontained also 18 g. of the original gauze and 53 g. of tobaccomaterial. The sheet was shredded and made into non-filter cigarettes ofRTD 3.0-4.2 and 1.0 g. filler weight. The cigarette yielded 8 puffs percigarette and had a static burning rate of 4 mm./min. The phenolsdelivery was 33.10 g./cigarette and the nicotine delivery Was 0.44.10-g./cigarette.

American non-filter cigarettes of the same length presently on themarket have a static burning rate of 4 to 5 mm./ min. and deliver 150 to180.10- g. phenols per cigarette and deliver 1.3 to 2.0.10 g. nicotineper cigarette.

This experiment demonstrates that both a material which bursts intoflame when lighted (cotton gauze cellulose) and a material which doesnot burn at all (oxidized cellulose gauze), when coated with tobaccomaterial and made into a cigarette, burn like an ordinary cigarette andyield low amounts of phenols and of nicotine.

What is claimed is:

1. A reinforced reconstituted tobacco sheet comprising a web woven oftreated cellulose having a weight of from 14 to grams per square yardand having 15 to threads per inch, said woven web having adhered theretofrom 1 to 20 parts by weight of particulate tobacco per part of saidtreated cellulose, said reinforced reconstituted tobacco sheet beingsuch that when it is incorporated with a cigarette, said cigarette has astatic burning rate of not less than 2 millimeters per minute and notmore than 5 millimeters per minute, said treated cellulose comprisingoxidized cellulose.

References Cited UNITED STATES PATENTS 2,805,669 9/1957 Merino 131-l432,934,073 4/1960 Killian 131l43 X 3,003,895 10/1961 Grunwald 13117FOREIGN PATENTS 702,918 2/1965 Canada.

MELVIN D. REIN, Primary Examiner US. Cl. X.R.

Inventor(s) Henri C. Silberman Attesting Officer It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 6 line 68, "an" should read -"and-- Col. 8, line 29, "was shouldread --were-- line 49, homogcnized' should read --homogenized-- line 57,"henzo(a) pyreue should read benz (a)pyrene-- and line 73,"Benzo(a)pyrene" should read Benz (a)p 'rene-- Col. 9, lines 4 and 6"benze (a)p 'rene should read --benz (a) pyrene-- line ll, "Ben'o(a)pyrene" should read Ben za)pyrene l0 /Clg' l g./cig.

Col. 10, line 65, Burn" should read Burnt- Col. ll, line 15 pentaerthrityl should read "pentaerythrito and. line 22 "was" should read"were" Col. 12, line 16 cholride' should read -chloride-- line 38,

was should gead --were-- and line 64, 18. 10 shou read 18x10 Col. 13,line 4 "22.10' should read "22Xl0 line 5,

"9.39- 10' should read --0.39X10 line 13, 33 10 should read "3 x10 linol4, "0. 4. 10 should read --0.44X10' line 17, 180.} should read 130x10"and line 1o, 2 .0.10 should read "'2.UxlO

SIGNED AND SEALEB W 121970 Attest:

Edward M. Fletcher, Ir.

' mum; 1:. m. Connnissioner of Patents

